The present invention relates to a gas operating device for releasing the locking of the breechblock by axially moving the action bar assembly mounted outside of the gunbarrel or the cartridge magazine tube located in juxtaposed relationship to the gunbarrel by utilizing the gas pressure generated at the firing of the shot shell in an automatic gun and succeedingly for causing recoiling the breechblock, and to a supporting mechanism for the gunbarrel and the fore-arm.
Many of the prior art automatic guns are of the type wherein the empty cartridge is extracted by the recoiling of the breechblock caused by utilizing the gas pressure generated at the firing of a shot shell and a new shot shell is loaded. However, the breechblock also exhibits the action to block the barrel extension of the gunbarrel, and the above described blocking state must be maintained until the gun powder is brought to its normal explosion condition after ignition thereof. To this end, the gun is so constructed that the movable body is displaced by the above described gas operating device by the medium of the gas pressure at a predetermined position of the gunbarrel so that the locking of the breechblock is released by the sliding movement of the action bar assembly and succeedingly the recoiling of the breechblock is effected at a predetermined time delay of the action.
Many of the gas operation devices provided in the prior art automatic guns of the type described above are so constructed that the cylinder housing therein a piston actuated by the gas pressure introduced therein from the gunbarrel is arranged at the front end portion of the cartridge magazine tube so that the sliding movement of the piston is transmitted to the breechblock through cylindrical action sleeve slidingly engaging with the cartridge magazine tube and thence through action bar integral with or arranged separately from the action sleeve.
However, the gas operating device constructed as described above has the following disadvantages:
When the action bar mounted integrally with the periphery of the action sleeve transmits the impact load from the piston acting against the action sleeve, a bending amount is given to the action bar so that the periphery of the action sleeve might rub the sliding surface of the cartridge magazine tube. Therefore, in order to withstand such actions, the action bar and the action sleeve must be made of a high strength material.
Further, when the action sleeve and the action bar are manufactured as separate members and they are joined together thereafter, the directions of force applied thereto are different from each other, so that it is necessary to maintain sufficient strength at the connecting portion thereof.
Further, in the gas operating device of the kind as described above, since the bottom portion of the receiver or the guide hole of the breechblock might be damaged or broken when unnecessarily large recoiling force is given to the breechblock by giving to the breechblock a sufficient force for automatically loading a shot shell to rearwardly move the same in the receiver and succeedingly forwardly advance the same for completing a series of operations (referred to hereinafter as "OPERATION"), the cylinder is so constructed that the gas is freed from the cylinder when the piston has been rearwardly moved a predetermined length. However, in case the gas pressure of the shot shell used is low, it might occur that a sufficient rotation is not given to the breechblock.
Further, the gas pressure generated at the firing of a shot shell differs largely depending upon the kind of the shot shell usually used, so that the delay in actuation of the movable body in response to the variation in the load acting thereagainst will become irregular or uneven. Thus, it is very difficult to insure a constant delay time of actuation of the action bar assembly by compensating for the gas pressure varying in a wide range.
The prior art gunbarrel supporting mechanism provided in an automatic gun is of the construction wherein the rearward end portion of the gunbarrel is inserted into an opening in the front end portion of the receiver housing therein the mechanism of the breechblock assembly by a predetermined length and either one the portion of the gunbarrel inserted into the receiver and the inner wall surface of the receiver is provided with a projection while a recess is formed in the other so that the engagement of the projection and the recess serves as the rotation arresting means, the bracket provided in the tip of the gunbarrel being attached to the cartridge magazine thereby preventing removal of the gunbarrel. Thus, the fore-end or fore-arm arranged outside of the gunbarrel and embracingly supporting the cartridge magazine is usually so configured that the ends of the both arms of the forward stock in the substantially U-shape in cross-section abut against the outer periphery of the gunbarrel along the generating line of the gunbarrel, and the rearward end portion of the fore-arm embracingly supports the side edge portion of the receiver so as to serve as the rotation arresting means, the removal of the fore-arm being effected at the forward end portion of the cartridge magazine barrel as in the case of the gunbarrel.
However, in the construction as described above, since the gunbarrel is supported in rotation preventing manner, a pair of projection-recess engaging portion must be formed in the gunbarrel and the inner wall of the receiver, thereby requiring a separate rotation preventing portion to be formed for the fore-arm. Thus, the machining operation is increased and the configuration of the rearward end portion of the fore-arm is limited because the rearward end portion must embrace the side surfaces of the receiver thereby restricting the freedom of design of the construction.